class_docstr: Begin(state_name) is a Plex action which causes the Scanner to
  enter the state |state_name|. See the docstring of Plex.Lexicon
  for more information.
code: def perform(self, token_stream, text):
      token_stream.begin(self.state_name)
  
label_desc: Use image node_id 2 for calling the Begin obj's underlying member method code with example usage: obj.perform(token_stream, text) without return types